The present invention relates to methods for manufacturing combination wrenches and, more particularly, to methods for manufacturing combination wrenches without generating carbon scale.
FIGS. 18 and 18A show a cylindrical bar 1 for manufacturing a combination wrench according to a conventional method. Specifically, bar 1 of a predetermined length is prepared by cutting. Bar 1 is heated to a temperature above 800° C. to soften for hot-forging. Upper and lower dies are then utilized to forge the softened bar 1 into a wrench blank 2 shown in FIG. 19. Since wrench blank 2 is still at a high temperature, waiting for the wrench blank 2 to cool down for subsequent processing is a waste section 3 and adversely affects the speed of manufacturing. Furthermore, layers of carbon scale are generated when the temperature of wrench blank 2 lowers to room temperature, and manual grinding for removing the carbon scale is required, leading to an increase in the manufacturing costs. Further, a considerable waste section 3 up to 50% of bar 1 is generated during forging of wrench blank 2, increasing the material costs. Further, it is difficult to control the thickness of waste section 3, such that the tolerance of wrench blank 2 is relatively high, reducing yield. Further, removal of the waste section 3 is not easy when clamping waste section 3 formed around wrench blank 2. Laborsome and time-consuming manual removal of waste section 3 by grinding is, thus, required.
Thus, a need exists for novel methods for manufacturing combination wrenches with less waste section of materials to avoid laborsome and time-consuming removal of the waste.